I like MP5, actually. I know people complain about how many Mario Party games there are but I was glad they made it, just because I wanted one for the Cube and Mario Party 4 was so terrible I like to pretend it doesn't exist. I'm not exactly on the edge of my seat for the next one or anything but there were some completely new features in MP5 that I enjoyed--for one thing, being able to play as Toad, Koopa Kid or Boo. That's just a little thing but I thought it was nice that they mixed it up a bit since all the other games have basically the same cast over and over again (plus or minus Daisy and Waluigi). Also, being able to play on teams is nice. And some of the new mini-games actually were different for once, and quite fun. I can go to mini-game mode and play 5-minute Piece Out over and over against a difficult computer character if I don't feel like having a "party," and it's like having a completely different game.
The music wasn't great though--usually there's at least one track I could listen to for hours on end (like the Bowser parade!) but not so here. The voices were annoying too, as were the capsule events.
I wouldn't go so far as to give it a 2, because it is fun, as long as you're playing with someone else. Maybe a 6 or 7. And no, we don't need an MP6, at least not until we get a new system (if we ever do).